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Reverse Correlation (reverse + correlation)

Distribution by Scientific Domains

Medical Sciences	25%

Selected Abstracts

Acid,Base Chemistry at the Ice Surface: Reverse Correlation Between Intrinsic Basicity and Proton-Transfer Efficiency to Ammonia and Methyl Amines

CHEMPHYSCHEM, Issue 17 2007
Seong-Chan Park Dr.
Abstract Proton transfer from the hydronium ion to NH3, CH3NH2, and (CH3)2NH is examined at the surface of ice films at 60 K. The reactants and products are quantitatively monitored by the techniques of Cs+ reactive-ion scattering and low-energy sputtering. The proton-transfer reactions at the ice surface proceed only to a limited extent. The proton-transfer efficiency exhibits the order NH3>(CH3)NH2=(CH3)2NH, which opposes the basicity order of the amines in the gas phase or aqueous solution. Thermochemical analysis suggests that the energetics of the proton-transfer reaction is greatly altered at the ice surface from that in liquid water due to limited hydration. Water molecules constrained at the ice surface amplify the methyl substitution effect on the hydration efficiency of the amines and reverse the order of their proton-accepting abilities. [source]

Reverse correlation in neurophysiology

COGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 2 2004
Dario Ringach
Abstract This article presents a review of reverse correlation in neurophysiology. We discuss the basis of reverse correlation in linear transducers and in spiking neurons. The application of reverse correlation to measure the receptive fields of visual neurons using white noise and m-sequences, and classical findings about spatial and color processing in the cortex resulting from such measurements, are emphasized. Finally, we describe new developments in reverse correlation, including "sub-space" and categorical reverse-correlation. Recent results obtained by applying such methods in the orientation, spatial-frequency and Fourier domains have revealed the importance of cortical inhibition in the establishment of sharp tuning selectivity in single neurons. [source]

Biochemical composition of the Atlantic bonito Sarda sarda from the Aegean Sea (eastern Mediterranean Sea) in different stages of sexual maturity

JOURNAL OF FISH BIOLOGY, Issue 2 2006
N. Zaboukas
The content (% wet mass) in water, ash, lipid, crude protein, DNA and RNA of different tissues was determined during sexual maturation of bonitos Sarda sarda from the Aegean Sea. A total of 220 specimens were collected in the following stages of sexual maturity: immature, resting, developing, mature, spawning and spent. Highest lipid levels in the white muscle, red muscle and liver were measured in immature specimens, while lowest levels were found in spawning bonitos. The gradual percentage of lipid reduction from immature to spawning bonitos was relatively higher in the liver (females 71·2% and males 64·4%) than in the white (females 59·2% and males 53·5%) and red (females 62·1% and males 51·7%) muscle. Lipid levels in the gonads increased gradually from the immature to spawning stage. The decrease of lipid in the somatic tissues was more intense in females than in males, and gonadal lipid content was higher in females than in males. There was a strong reverse correlation between water and lipid percentage in all tissues. Protein content decreased significantly only in spawning bonitos. The percentage of protein reduction from immature to spawning stage was relatively higher in males than in females in both white (females 3·4% and males 4·6%) and red (females 4·6% and males 5·1%) muscles. Protein content in the liver was significantly lower than in the other tissues, being highest in mature females. Gonadal protein content in females increased with maturation and decreased after spawning. The content in ash exhibited considerable stability. The RNA:DNA ratio exhibited a similar pattern of variation in both muscles. The RNA:DNA ratio increased during gonadal development gradually from the developing to spent stage. It was concluded that in S. sarda during gonadal development, there was an increase in gonadal lipid accompanied by a decrease in somatic tissue lipid reserves. Thus, reproductive inactive bonitos have more lipid in their edible part and a higher nutritional value than active ones. [source]

Helicobacter pylori eradication therapy modulates acidity and interleukin-1, mRNA levels in un-operated stomach and in remnant stomach after gastrectomy in gastric cancer patients

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 2006
S. KATO
Summary Background A number of studies have indicated that Helicobacter pylori eradication therapy helps prevent secondary cancers in the stomach. Aim To investigate the risk of secondary cancer in the residual stomach after gastrectomy by comparing molecular biomarkers from stomach mucosa biopsies and the pH of gastric juice between H. pylori patients with and without gastrectomy. Methods Conventional H. pylori eradication therapy was administered to 22 patients who had undergone gastrectomy and to 37 un-operated patients. We measured pH levels of gastric juice, and collected stomach mucosa biopsy specimens by gastrointestinal fiberscopy. The mRNA expression levels of interleukin-1,, interleukin-8 and cyclo-oxygenase 2 in the biopsy tissues were measured by real-time polymerase chain reaction. Results Interleukin-1, levels in the antrum of un-operated H. pylori -positive patients showed a reverse correlation with pH levels in the gastric lumen (correlation coefficient: ,0.50, P = 0.007). After eradication, pH levels were strongly associated with interleukin-1, mRNA levels, r = 0.83, P = 0.01, which, in the remnant stomach mucosa, decreased from 22.5 to 4.6 in the anastomosis and from 3.1 to 2.4 in the upper corpus, with a simultaneous and statistically significant decrease in pH. Conclusions Interleukin-1, mRNA levels correlated with pH levels in the remnant stomach. This indicates that eradication therapy may contribute not only to a reduction in these cancer-associated cytokines, but also to an improvement in the internal environment of the remnant stomach. [source]

Contributions of the input signal and prior activation history to the discharge behaviour of rat motoneurones

THE JOURNAL OF PHYSIOLOGY, Issue 3 2005
R. K. Powers
The principal computational operation of neurones is the transformation of synaptic inputs into spike train outputs. The probability of spike occurrence in neurones is determined by the time course and magnitude of the total current reaching the spike initiation zone. The features of this current that are most effective in evoking spikes can be determined by injecting a Gaussian current waveform into a neurone and using spike-triggered reverse correlation to calculate the average current trajectory (ACT) preceding spikes. The time course of this ACT (and the related first-order Wiener kernel) provides a general description of a neurone's response to dynamic stimuli. In many different neurones, the ACT is characterized by a shallow hyperpolarizing trough followed by a more rapid depolarizing peak immediately preceding the spike. The hyperpolarizing phase is thought to reflect an enhancement of excitability by partial removal of sodium inactivation. Alternatively, this feature could simply reflect the fact that interspike intervals that are longer than average can only occur when the current is lower than average toward the end of the interspike interval. Thus, the ACT calculated for the entire spike train displays an attenuated version of the hyperpolarizing trough associated with the long interspike intervals. This alternative explanation for the characteristic shape of the ACT implies that it depends upon the time since the previous spike, i.e. the ACT reflects both previous stimulus history and previous discharge history. The present study presents results based on recordings of noise-driven discharge in rat hypoglossal motoneurones that support this alternative explanation. First, we show that the hyperpolarizing trough is larger in ACTs calculated from spikes preceded by long interspike intervals, and minimal or absent in those based on short interspike intervals. Second, we show that the trough is present for ACTs calculated from the discharge of a threshold-crossing neurone model with a postspike afterhyperpolarization (AHP), but absent from those calculated from the discharge of a model without an AHP. We show that it is possible to represent noise-driven discharge using a two-component linear model that predicts discharge probability based on the sum of a feedback kernel and a stimulus kernel. The feedback kernel reflects the influence of prior discharge mediated by the AHP, and it increases in amplitude when AHP amplitude is increased by pharmacological manipulations. Finally, we show that the predictions of this model are virtually identical to those based on the first-order Wiener kernel. This suggests that the Wiener kernels derived from standard white-noise analysis of noise-driven discharge in neurones actually reflect the effects of both stimulus and discharge history. [source]

Reverse correlation in neurophysiology

Gastrin suppresses the interdependent expression of p16 and anion exchanger 1 favoring growth inhibition of gastric cancer cells

INTERNATIONAL JOURNAL OF CANCER, Issue 6 2010
Hua Tian
Abstract Our previous studies demonstrated that expression and interaction of p16 with anion exchanger 1 (AE1) in gastric cancer cells is correlated with progression and shorter survival of the cancer. In this article, the effects of gastrin on p16 and AE1 and its implication in prevention and treatment of gastric cancer were studied by molecular biology techniques, animal experiment and clinical analysis. The results showed that expression of p16 in human gastric body carcinoma was downregulated along with the progression of the cancer, suggesting the reverse correlations between gastrin and p16 in vivo. Further experiments indicated that gastrin suppressed the expression of p16 via the p16 promoter and thereafter resulted in the degradation of AE1 in gastric cancer cells. Silencing of AE1 or p16 significantly inhibited the proliferation of the cancer cells. Using a xenograft tumor model in nude mice, we showed that experimental systemic hypergastrinemia induced by the administration of omeprazole led to decreased expression of AE1 and p16 as well as to a marked growth inhibition of SGC7901 tumors. It is concluded that a moderate plasma gastrin level is beneficial to the growth inhibition of gastric cancer by suppressing the expression of AE1 and p16. This finding may have an important implication for the prevention and treatment of cancers arise in the gastric antrum. [source]

Occupational Stress and Psychological Well-Being in Emergency Services

ASIAN SOCIAL WORK AND POLICY REVIEW, Issue 3 2009
Mohd Dahlan A. Malek
Sources of occupational stress and their impact on job satisfaction and psychological well-being were examined in a questionnaire survey of 617 Malaysian firefighters. The role of coping strategies and work motivation as moderating factors were also tested. Sources of occupational stress had significant reverse correlations with job satisfaction and well-being. The hierarchical regression analysis was used to examine the moderating effect of work motivation and coping strategies on job satisfaction and psychological well-being. The result suggested that coping strategies and work motivation are one of the potential moderating variables between sources of stress and job satisfaction. [source]